Cellular telephones and music-playback devices frequently are sold as a package, including the hand unit (the phone), a charger and earphones. Because earphones are so routinely supplied by manufacturers, they are increasingly used with small mobile devices such as cellular telephones and music players. While “over-the-ear” phones are known, smaller “ear bud” earphones are more commonly used. Such stereo earphones may include a 3.5 mm plug (or similar) for attachment to the cell phone.
However, while earphones are quite common, they are also somewhat limited in functionally. As a result, only limited use is made of the earphone jack into which they are connected.